A/C switching on and off randomly and car is overheating after running
Buick LeSabre 2004 91368 miles
The A/C is 'bipolar' it will switch on and off randomly and the car overheats after running for a while. We have checked the Freon with a gage and its good. We have replaced the thermostat so its new. We replaced the blower motor at an earlier time because the air stopped blowing completely so that's new. We are still going down the list of items to check but id like some info from others who may have this problem. The fans seem to work as they come on when it gets to hot and come on when the car is off but they might be shutting off randomly we just haven't confirmed that yet. Coolant is good and the radiator is full but we may replace the radiator cap because we were told that might be a problem. Next on the list is the sensors, water pump and compressor. The compressor is switching on though. And to note, weirdly if I "play" with the window switches the A/C will burst some cool air and also when i turn the wheel left or right and when i press on the break. We will be checking fuses today and honestly we should have started with that but oh well.
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The fact that the A/C behavior changes when Dominoxic uses the window switches, turns the steering wheel, or hits the brakes is a "smoking gun" for a bad ground connection. The Problem: These cars use several "grounding bus bars" (often located under the carpet or near the kick panels) that are notorious for corroding or getting wet. The Result: When one system (like the power windows) draws current, it "backfeeds" through other circuits (like the A/C clutch) because it can't find a clean path to the frame. Action Step: Check the ground wires near the battery and the grounding blocks inside the front passenger and driver-side kick panels. Look for corrosion or "green crust". 2. The Overheating and A/C Connection
The A/C and the cooling system are linked by the Engine Cooling Fans. The Fans: The A/C compressor requires the cooling fans to run to dissipate heat. If the fans are "shutting off randomly" as suspected, the A/C high-side pressure will spike, and the computer will force the compressor off to prevent it from exploding. The Overheating: If those same fans aren't staying on consistently, the car will overheat while idling or in stop-and-go traffic. The Likely Culprits: * Fan Relays: There are three relays in the under-hood fuse box that control low and high speeds. These often burn out. Fan Motor Connectors: Check the actual plugs going into the fans; they often melt or develop loose pins. 3. The PCM Safety Cut-off
On this 3.8L engine, the Power Control Module (PCM) will automatically disable the A/C compressor if the engine temperature exceeds a certain threshold (usually around 225°F–230°F) to reduce the load on the engine. The A/C switching off might not be a fault of the A/C itself, but a symptom of the overheating. Recommended Troubleshooting Steps for Dominoxic:
Clean the Battery Terminals and Main Grounds: This is the cheapest and most likely fix for the "window switch" weirdness. Test Fan Relays: Swap the fan relays with known good ones (like the horn relay) to see if the fans stay on consistently. Check for "Air Pockets": Since they replaced the thermostat, there might be air trapped in the system. These engines have a bleeder screw on top of the thermostat housing that must be opened to let air out while the engine is running. On the 2004 Buick LeSabre, there are two primary grounding bus bars (often called "splice packs") that are notorious for corroding due to moisture getting trapped under the carpet. These are the most likely cause of the "bipolar" electrical behavior Dominoxic is seeing. Primary Ground Bus Bar Locations:
Front Passenger Side: This is the most common failure point. It is located under the door sill plate or tucked just under the carpet near the bottom of the kick panel. Driver Side: A matching grounding block is located in the same position on the driver's side, under the door sill trim. Appearance: They look like small, black plastic rectangular blocks with a dozen or more black wires plugged into them. They are bolted directly to the metal floor pan or inner rocker panel.
Why this explains the symptoms:
Window Switches: The power window motors draw high current. If the ground bus bar is corroded, that current can't exit to the frame easily. It "backs up" and flows into other wires in that same block—like the ones for the A/C controls or the PCM—causing the A/C to glitch or surge when the windows are used. Steering and Brakes: Turning the wheel (Power Steering Pressure Switch) and hitting the brakes (Brake Lamp Switch) also send signals through these grounding points.
"Dominoxic, you need to pull up your door sill plates and peel back the carpet. Look for a small black plastic block with many black wires. If you see 'green crust' or white powder around it, that's your problem. Unbolt it, clean the metal on the car and the metal tab on the block with a wire brush, and re-secure it. This should stop the A/C from acting up when you use your windows or brakes. "
I also have a weird problem with my radio where I can only barely hear static and the faint sound of the radio even if it’s on full blast